1. Field of the Invention
The present invention is related to a multilayer structure employed in hybrid IC (integrated circuit) or semiconductor devices, etc. More particularly, the invention is related to a reliable method and means for electrically interconnecting conductive layers having an insulative resin layer disposed therebetween.
2. Description of the Related Arts
Many kinds of multilayer structures and fabrication methods have been employed for fabricating hybrid ICs (integrated circuits) and semiconductor devices. A typical structure and manufacturing method are described in Japanese Unexamined Patent Publication Sho-63-244796 and shown here in FIG. 1. In accordance with this method, a wiring pattern 31 is formed on a first electrically conductive copper layer 38 that is disposed on an insulative glass substrate layer 37. The wiring pattern 31 is formed using a first resist pattern 32. A second resist pattern 33 having a hole 34 located above wiring pattern 31 is formed on resist pattern 32 (FIG. 1a) and a pillar 35 is formed in hole 34 by an electroplating. The first and second resist patterns 32 and 33 are removed and then a polyimide resin layer 36 (FIG. 1b) is formed over pillar 35, wiring pattern 31 and conductive layer 38. The top of pillar 35 is exposed by polishing or etching the surface of the polyimide resin layer 36 and a second electrically conductive layer 38' (FIG. 1c) and a second wiring pattern 31' (FIG. 1d) are formed over polyimide resin layer 36 and the top of pillar 35.
The spirit of this prior art structure is to flatten the top of pillar 35 as can be comprehended from the foregoing description and from FIGS. 1(b) and 1(c). However, when the top of the pillar is flat the electrical contact between the pillar top and electrically conductive layer 8 is not strong enough to withstand the mechanical stresses resulting from heating cycles, etc. This presents a possibility that the connection will break resulting in a deterioration in the reliability of the electrical connection between the multiple layers. Moreover, if the pillar top is flattened by mechanically polishing the surface of insulative layer 36, the polishing operation is very difficult because the substrate might have a tendency to bend due to the presence of the polyimide resin coating.